Abstracts

RATIONALE: Electroencephalograms (EEGs) are routinely requested for patients in unresponsive states. We studied the various EEG patterns occurring in unresponsive adult and pediatric patients to aid in their diagnostic evaluation. At the end of this activity the participants should gain an understanding for EEG patterns in adult and pediatric patients in unconscious states and their potential etiologies.
METHODS: The EEG patterns of unresponsive patients between the ages of 1 day and 101 years were analyzed. The EEG studies were requested by intensivists and neurologists for patients admitted to intensive care units. The EEG interpreters were unaware of the patients[ssquote] clinical diagnoses. EEG background patterns and epileptiform activity were determined. Patients in whom unresponsiveness could be attributed to pharmacological agents were not included. All EEGs were performed utilizing the standard recommendations of the American EEG Society.
RESULTS: A total of 610 EEG studies (from 119 children and 491 adults) were analyzed over a two year period. The mean age of the patient population was 56.7 years. The following EEG patterns were observed:
1. 137 patients (23%) had EEG patterns consistent with nonconvulsive status epilepticus (NCSE). The incidence of NCSE was higher in the pediatric population (33%) compared with the adults (20%).
2. Of the patients with NCSE, 47 patients (8%) had generalized NCSE and 90 patients (15%) had complex partial NCSE.
3. Of 119 children, 20 (17%) had generalized NCSE and 19 (16%) had complex partial NCSE. Of 491 adults, 27 (6%) had generalized NCSE and 71 (14%) had complex partial NCSE.
4. Of the 610 patients, 470 (77%) had only diffuse cerebral dysfunction, without evidence of NCSE.
5. Of the patients with diffuse cerebral dysfunction, 118 (25%) patients had interictal epileptiform activity.
6. In patients with diffuse cerebral dysfunction, 121 patients (26%) had triphasic waves, suggesting a metabolic encephalopathy. This was much more common in the adult population (24%) compared to the pediatric patients (4%).
7. In 22 patients (4%), alpha coma, theta coma or burst suppression pattern was observed.
CONCLUSIONS: 1. NCSE is a common EEG pattern in unresponsive patients, particularly in the pediatric population.
2. Generalized NCSE is more common in unresponsive pediatric patients compared to adults. However, the incidence of complex partial NCSE is not significantly different between these groups.
3. A moderate to severe disturbance in cortical function was seen in the majority of our patients in an unresponsive state.
4. The existence of triphasic waves, which could indicate an underlying metabolic encephalopathy, is not an uncommon finding in adult patients with diffuse cortical disturbance. In contrast, the EEGs from unresponsive children in our study rarely had triphasic waves.
5. Routine EEG is a valuable diagnostic tool for patients with unexplained unresponsiveness in all age groups. The difference in EEG findings in different age groups is not only an interesting neurophysiologic phenomenon, but can also aid in the clinical management of these patients.